In Twisty Little Passages, Montfort distinguishes between three types of story or narrative: Diegetic, Hypodiegetic, and Extradiegetic (from diegesis). The 1001 Arabian Nights is useful for describing the differences: The framework story is diegetic, each of the individual stories is hypodiegetic, and the physical book itself, the paper and ink, is extradiegetic.
In the world of Interactive Fiction, Diegetic commands are those which control the “player character”. Extradiegetic (e.g. meta-) commands are those which control the game itself. Hypodiegetic commands are those which are made through the player character, and which influence other characters in the game.
Moving from Interactive Fiction out to User Interaction, we find some parallels. Using the navigation links in a website is diegetic. Using the web browser controls is extradiegetic. Perhaps using in-system tools (e.g. a price calculator or a store locator) could be considered hypodiegetic.
Someone pointed out a few years ago that web developers and usability experts, nominally working in a “new” field, could take many lessons from the video game industry, which has been working on many of these same problems for more than 30 years.